Reflector



.pi Z, 1936. M Wl CAUGHLAN REFLECTOR Filed March 7; 1928 n 4 Sheets-Sheet mc vom INVENTOR.

ByLLJw/w TORNEY April 29, 1930.

M. W. CAUGHLAN REFLECTOR Filed March 7, 1928 4 Sheets-Sheet )mi mgl VENTOR. g/.LQ y# April 29, 1930.

M. W. CAUGHLAN REFLECTOR Filed March '7, 1928 4 Sheets-Sheet 3 INVENTOR.

April 29, 1930. Y M W, CAUGHLAN 1,756,084

REFLECTOR Filed March 7, 1928 4 Sheets-Sheet 4 INI/ENTORL Patented Apr. 29, 1930 PATENT OFFICE i MARTHA W. CAUGHLAN, OF OAKLAND, CALIFORNIA BEFLCECTOR Application led March 7,

My invention has for its objecta reflector adapted to collect the light emanating from a light source and reflect the same and by a single refiection to cause all of the reflected rays to pass out crossing on a focal line and within predetermined limits.

A further object is a refiector of the character described having upper and lower portions wherein the reflected rays from the upper part of the upper portion and from the lower part of the lower portion are directed downward with respect to the rays emanated from the lower part of the upper portion and from the upper part of the lower portion.

A further obejct is a reflector of the character described having an end closure with a relatively narrow li ht emanating aperture 'ubstantially coinci ent with the said focal ine.

A further object is a reflector of the character described wherein 'a plane glass front is employed through which the re ected ra s are transmitted and which glass is relative y narrow and long and wherein the said glass is inclined with respect to the horizontal axisof the refiector.

Other objects will appear from the drawy ing and specification which follow.

These objects I attain by forming my reflector surface in two portions joined together preferably at the common elliptical periphery, which I have called in my description below, the master ellipse.

The lower reficctor surface (below the said master ellipse) is formed of successive and diminishing ellipses lying in planes at successively increasing angles with the plane of I the master ellipse as the ellipses descend and diminish, and said ellipses have minor axes 4 parallel with the minor axis of the master ellipse.

The up er portion of the reflector 1s also formed of) ascending diminishinfr ellipses of increasing inclination to the p ane' of the master ellipse', and all of said ellipses having their minor axes parallel with the minor axis of the master ellipse.

The vertex of the angle of inclination'o the upper ellipses falls on the extended major axis of the master ellipse on one side and the i928. serial Nu. 259,697.

sectiontlirough one form of the lampv of my invent-ion.

Flg, 3 is a horizontal mid-section and Fig.

'4 is a front view of the lamp of Fig. 2.

Fig. 5 is a diagrammatic illustration of the ifnethod of producing the lower reflector surace.

Fig. 6 is a diagram in plan of one half of the master ellipse of Fig. 5. Y

Figs. 7 and 8 are other elliptical sections of successive ellipsoids taken at right angles to the paper of Fig. 5 and through different 75 portions of the lower refiecting surface.

Fic. 9 is a space diagram showin the conic relation of the several curves of the ower p0rtion of the reflector of Figs. 2 3, 4:.

Figs. l0 and 1l are space diagrams of the 80 several conics of the upper portion of the reflector'of Figs. 2, 3, 4.

Fig. l2 is a space diagram combinin in a single ligure the principal conics of Flgs. 9,

5 and 1l of the upper and lower portions of 85 the reflector.

Fig. 13 is a perspective view of an illuminated surface in front of the lamp.

Throughout the figures similar numerals refer to identical parts.

The upper portion of one form of the lamp of my invention is shown generally by the numeral l and the lower portion by the numeral 2.

Assume that it is desired to distribute the' 95 entire illumination from the lower half lamp as a band of light whose upper limit shall be the horizontally projected ray 3 and whose lower limit shall be the downwardly projected ray 4 and whose lateraldispersion shall 100 .See Figs. 3 and 5.

be between the extreme limiting rays '34,' 46.

First draw the line 4 through a point 7 such that the distance 7, 8 will give the desired dimension to t-he front portion of the completed lamp. Continue the line 4 until it intersects. the line 3 at a point 9 (see Figs. 1 and 9). i g

With the point 9 as a center and the line 7--9 as a radius describe the circular arc 7,

v10; choose now a point 11 which is to be the light source ofv my reflector. About the points 10, 11 as foci construct an ellipse 12 with major axis 14-13 which will give the desired size to the finished lamp and give the desired lateral light dispersion between the rays 46, 34 asl shown in Figs. 3 and 10. Such an ellipse is indicated at 12 having vertices 13, 14.

On the circular are 10-7 take any other vpoint as 15, draw aline through 15-11 and lay 0H thereon the line 16--17 equal in length tothe major axis 13--14 and such that 11-y-17 Y equals 15-16. Construct on the line 16-17 as a major axis the ellipsoid whose trace is the ellipse 18 and whose fociare 11, 15 respectively.

Pass a plane through the line 19 perpeni di'cular to the plane of the paper and passing through the points 15 and 9 it will cut the ellipsoid 18 in an ellipse 58, which ellipse in lan will be as shown in Fig. 7. Every point in such ellipse is common to its corresponding ellipsoid surface.

In the same way select any other point as 20 and with the same length of major axis as 13, 14 and with the foci 2,0-11 describev the ellipsoid whose trace is the ellipse 21 and cut this with a plane through line 22 perpendicular to the plane of the paper of Fig. 5

then be out an ellipse such as 58, and'51, theand passing through the focus 20 and the point 9, this plane 22 will then cut the ellipsoid 21 in the ellipse 51 of Figs. 5 and'B. In

like manner conceive ellipsoids all having the same major. axis equal to the line 13--14 and all having the same common-focal point 11, but whose remote fooi lie upon the circular arc 107. Cut each of these ellipsoids with a plane passing through its remote focus, as 15-20 and through the point 9.

From each of these ellipsoids there lwill largest of these ellipses will be the master ellipse 12 and the smallest will be the point A7. The ellipses will decrease in'l magnitude and increase in eccentricity as they descend trol? the remote focus 10 to the remote focus The lower surface of my reflector is made up of an infinite number of such ellipses as 12,58, 51 etc. every point in which is commonV to its corresponding ellipsoid, all of which have a common focus 11.

All of the reflected rays from the lower I portion of the reflector will now issue in the planes of these respective ellipses which pass through the point 9 and will be confined between the horizontal plane of ray 3 and the downwardly directed plane through line 4 and in prooi:I thereof note that a ray of light originating at one of the foci 11 of an ellipsid, will be reflected from every point 'within said-ellipsoid and therefore every point on its ellipticalsection which has been chosen and will pass through the other elvlipsoid focus' which by construction is located lon the are 10, 15, 7 and my surface is con.-.

structed of an infinite number of such in- `clined diminishing elliptical sections.

Note that every point on every one of the ellipses as those shown in Figs. 6, 7 and 8 is a point on an ellipsoid, one of whose foci is on the arc 10-7 and inthe plane of the respective ellipse and in which plane the corresponding reflected rays will issue.

For example referring to Fig. 6, a light ray originating at 11 will be reflected at 30 passing through the focus 10 and emerging as the ray 31. Likewise a rayreflected from 11 at the point 54 will issue as the ray 32 also passing through the focus 10 and a ray from 11 to the point 33 will issue as a ray 34 also passing .through the focus 10, and all in the plane of the figure and of the ellipse 12.

The ellipse 58 vof Fig. 7 which is cut from the ellipsoid whose tracer is 18 (see also Fig. 5) by the plane through the line 19 is entirely made up of points all taken from the said ellipsoid` 18 whose proximate focus is 11 and whose remote focus is '15 and such points will therefore reflect from any point 40 a ray originating from the light source 11 through the remote focus 15 and issue as the ray 41,

and will all lie in the plane of the paper of Fig. 71and therefore in the plane 19, 9 perpendicular to the plane of the paper of Fig. 5, likewise the ray originating at the proximate focus 11 will be reflected from the point 43 on the ellipsel of Fig.'8 through the remote focus 20 as indicated at 44.

The same is true of every other point down to and including the point 7 into-which the diminishing ellipsesl cut from their respective ellipsoids at last are merged.

The rear vertices of all of the inclined el-` lipses above described lie upon one branch of an hyperbola.

Applying the law of thefhyperbola, that the`-` difference between the distance of any point thereon from the remote and from the proxi' mate foci, is equal to a constant, and referring particularly to Figs. 5 and 9, the two hyperbolic foci are 9 and 11 respectively. The

point 13 will be one pointupon `the branch 45 of such a. hyperbola, and 9, 13 minus 1l, 13 which is plotted in Fig. 5 at the point 87, will be the hyperbolic constant and is equal to 9,

87, that is the radius of the circular arc 79,

struck from 9 as al center, and is concentric with the are 10, 15, 7, and distant therefrom i. perbola.

The curve 14,-90,; 91, 7 traced by the vertices of theV descending ellipses as 58, 51, each cut from its corresponding ellipsoid, is an arc of an ellipse 88, having the foci 9 and 11. The distance 9, 10 plus .10, 14, plus 14, 11 is the vmajoraxis of the ellipse 88, and the arc 10, u. 15, 20, 7 being struck from a center 9, every point thereon is at a constant distance equal to`9, 10 from 9.

' ellipse.

To prove that curve 14, 90, 91, 7 is an arc of ellipse 88. If We take any point as 90 on said curve, and prove that 90, 11'plus 90, 9 equals 100, 14, a constant quantity such condition satisfies thelaw of the ellipse-see Figs. 5 and 9. Now, 90, 11 plus 90, 9 may be written as 90,11 plus 90,15 plus 9,'15; but 90,11 plus 90, 15 equals 13, 14 because point 90 is in the ellipsoid 18; also 9, 15 equals 9, 10 because they are radii of a circle whose center is 9;

hence 90, 11 plus 90, 15 plus 9, 15 equals 13,

14 plus 9, 10. Referring to Fig. 9; 100, 14 may be written as 100, 9 plus 9, 10 plus 10, 14

' which is equal to 9, 10 plus 13, 14. Hence 90,

11'plus90', 9 equals 100, 14, the major axis of ellipse 88 and point 90 is therefore on said The same will hold true with any other point onthe are 14, 90, 91, 7 and hence said arc is a lportion of the ellipse 88.

A preferable form for the upper portion of my reflector is one which shall ycollect all rays not heretofore reflected upon the lower described portion and after a single reflection of said rays will project them upon the same surface as the rays emanating from the lower reflector at a predetermined and substantial distance in front of the said reflector. In other words the, reflected beam from` the upper lamp portion will be superimposed upon the beam previously described and as indi'- cated in Fig. 1.

To attain such a surface on the line 3, choose the p`oint 59 and for simplicity in calculations such that the distance 59-7-10 shall be equal to the distance 10-9 and/construct a circular arc about 59 as the center and passing through the point 10. This is indicated I .in Figs. 11 and 12 by the arc 61-10. v

With the distance 13-14y (which is the major axis of the master ellipse of F ig.v 5) and with 11- as a center describe an arc and choose thereon any point 6l, draw any other line through 59 and between 61 and 10, it will intersect said arc at some point 63. Where it intersectsthe arc at 63 draw the line 66, 63, 65 through 11.

yWith 11 as a proximate focus and 63 as a remote focus construct an ellipsoid whose trace will be 69 and whose major axis 66, 65 is equal to the line 13, 14 and a plane 59-63-67 normal to the paper will intersect said ellipsoid in an ellipse and every point in which as demonstrated above in connection with the lower portion of my reflector will reflect light originating at the proximate focus 11 such that it will pass through the point 63 and emerge on the aforesaid plane 59-67.

Another such ellipsoid whose trace is the ellipse 7 0 andwhose major axis is 71, 72 will be cut by a plane normal to the paper through 59, 68. rlhe points 67, 68 respectively will be vertices of two such elliptical sections and will lfie upon the rear of the upper reflector surace.

The upper portion of my reflector is composed of an infinite number of such ellipses cut from their respective ellipsoids, all of which ellipsoids have a constant major axis, namely equal to the major axis 13-14 of the `master ellipse 12 of 5, and all will have a common focus 11. t

Every ray of li ht reflected from the upper portion of my re ector will therefore emerge in a plane normal to the plane of the paper.

The remote foci of the several ellipses will lie upon the circular arc 10-63-61 having 59 as a center.

The proximate vertices of each of the said ellipses will lie upon the curve 13, 67, 68, 61, and this curve will be a segment of an ellipse whose foci are l1 and 59.

As proof that this curve is an elliptical segment note that the distance from 11 to any point on any of the ellipses plus the distance,

from the vsaid point to the circular arc 61, 63, 10 Will be a constant. because they satisfy the law of the ellipse and the distance from the said circular arc to the point 59 is a constant by construction.

The sum of these two constants is of course constant and this satisfies the definition of an ellipse.

The remote vertices of the inclined ellipses of the upper reflector portion will lie upon' an hyperbola 61, 14. This will be evident from the fact that a similar group of ellipses in the lower reflector have their remote vertices upon an ellipse and their roximate vertices upon an hyperbole whic are confocal ,at 9 and 11 whereas in the upper half, the proximate vertices lie upon an ellipse with line is all that is necessary to admit of all of the rays passing out.

The thickness of the glass employed to cover the said aperture maybe made relatively thin flector may be removed and an obscure end portion 47 #-47 placed thereover, said end por- ,v tion containing only a'cnarrow vertical apen lo ture as shown at 48, being substantially-.oli

and narrow as it is seldom necessary to illumi-v A nate a horizontal angle as wide as that indicated between the lines`34 and 46 of Fig. Gbut rather that in commercialpractice outgoing rays'ibetweenmuch'narrovver limits may be employed.` Theforvvard portion of the rcthe 4focal 4line 6l', 63, 10, 15,20, 7;

The narrow glass front inthe slot 18-W1ll bey substantiallynormal to the mean ray in the reflected' beam, and Willbe directedV down.v

wardly;V that'is, the: glass front will beinclined forward. from'the vertical (see F1 s. 2

' and 12X-and therefore it'willnot reflect ack rays from their .own headlights -to drivers along the road and in front of my light.

It will now be seenthat every ray of light from the source 11 and which impinges on anypoint of the reflecting surface will be reflected of the total candle but `oncefand emerge through the inclined aperture 48'and-Wil1 be confined beyond the oint 59 within the vertical limits 3 and 4 and etween the horizontal limits `34. 46 of Fig. 1.0.

For examplereferri-ng to Fig. 3 there will besubstantially 99% of the-spherical candle power from `11- reflected andl projected within thesaid limits. v Y ,It is also to be observed that fifty per cent ower from the light source- 1'1 will be re ected from those surl face portions to the left-of a vertical lane tween the v,vertical limits 3 and 80 and the through v11 in Figs.2 and Band that the eam of this reflection will be comprised'be-I horizontal limits 82 and 83.

. The illuminated surface in front-ofthe4 lamp will therefore receive substantially 99%- of the original light from the source ll-and this will be concentrated in the proportion of 50% of saidA light within substantially 1 15 of said illuminated area (see 84 Fig. l0) and ing central, and all of said illumination ber* 49%-0ver the remainin 14/15 of said area (see85'of Fig. .10) the righter portions being below the horizontal plane of the linel.

\ The reflector above described and ishownfiny the figures as embodying one for-nr'of my in# vention isa'preferred form but from the de-l Y scription it-will be apparent that various other basic dimensions' may be usedas the distance betweenthe foci, the` distance/of the point 7 below the line 3, the position of the point 61 above the line 3, and by my method,

` reflecting. surfaces may be constructed securing the desired result without departing from my invention and I desire Lto be understood as c claiming-all such.

While I have shown and described my re# fleeting surface .as constructed about a lon'- gitudinal plane and employed the term vertical plane these are to bev considered only 'c as descriptiveand relative to the' drawing hand; it is to be understood that the reflecting surface may be moved into any other position or angle or rotated as the caseV may be.

1. A reflecting surface formed of a family of diminishing ellipses, said ellipses produced by the intersections of a family of ellipsoids with a pencil of planes, `said ellipsoids having a common proximate'focus and havingY remote foci on a vertical arc drawn from a center on the axis of and to the rear of said surface and said pencil of planes drawn through said center and said vremote foci respectively. f

2. A reflecting surface consisting of a family of diminishing ellipses Whose remote foci lie in 'a vertical arc drawn from a center on the axis'of and vto the rear of said surface and whose rear vertices lie on an hyperbolic arc.

3. A reflecting surface as set forth in claim -1 wherein the said arc is'normal to the said planes.

4; A reflecting surface as set forth in claim 2 wherein the said arc is normal to the said ellipses.

5. A reilecting'surface formed of a family of diminishing ellipses, said ellipses produced by the intersections of a family of ellipsoid-s with av pencil of planes, said ellipsoids having a. common proximate focus and having kremote foci on an arc drawn from a center on the axis of and forward of said surface and said pencil of planes drawn through said cen#` vfacefportio'n Aformed of a family of diminishig ellipses, said ellipses produced by'the intersections of a family of ellipsoids with a pencil of planes, said ellipsoids having a common proximate focus and having remote foci on avertical are drawn from a center on Vthe axis of and to the rear of said surface and said pencil of planes drawn through said cenf ter and said remote foci respectively, and

having another reflecting surface portion.

formed of a family of diminishing ellipses,

said ellipses produced by the intersections of a secondA family of ellipsoids with a second y' pencil of planes, said ellipsoids having the said common proximate focus and having remote foci on a vertical arc drawn ,from a ydifferent center on the axis of and forward of said surface and said second pencil of planes drawn through said different center and said remote foci respectively.

10. A reflector comprising a reflecting surface portion consisting of a family of diminishing ellipses Whose remote foci lie in a vertcal arc drawn from a center on the axis of and to the rear of said surface and whose rear vertices lie on an hyperbolic arc, and having another reflecting surface ortion consisting of a family of diminishing ellipses whose remote foci lie in a Vertical arc drawn from another center on the axis of and forward of said surface and Whose rear vertices lie on an elliptic arc.

11. A light projector comprising a light source7 a reflecting surface positioned about said light source, every point on which surface is positioned such that its distance from said light source plus its distance from a circular arc forward of said light source and struck from a center to the rear of said light source` is a constant7 said circular arc being vertical and lying in the median longitudinal plane of the reflecting surface.

MARTH W. cAUeHLAN. 

